Electric discharge device



y 26, 1932- H. M. MARTIN 7 .ELECTRIC DISCHARGE DEVICE Filed D90. 28, 1929 Fig.

Inventor Harold M. Martin,

by MW His Attorney- Patented July 26, 1932 UNITED STATES PATENT OF'FICE HAROLD M. MARTIN, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC DISCHARGE DEVICE Application filed December 28, 1929. Serial No. 417,208.

My invention relates to electric discharge devices provided with a liquid electrode, and has for its principal object the provision of an improved apparatus and method of control whereby such devices may be readily put into operation.

In the control of electric discharge devices, such as mercury arc rectifiers or the like, it is customary to produce a starting are which is transferred to the main electrodes or to the exciting electrodes when operation of the apparatus is initiated. Various means have been provided for producing this starting arc. Among these means are mechanisms for tilting the evacuated Vessel of the device and devices for moving the starting electrode or for applying an abnormally high starting voltage between the main electrodes of the device. Such means for producing the starting are have not been altogether satisfactory for the reason that they involve movement of the evacuated vessel or the provision of more or less complicated starting mechanisms and devices. In accordance with my invention this diiiiculty is avoided by the provision of magnetic means which are utilized to move the liquid electrode so as to produce temporary contact between it and a starting electrode.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 shows a rectifying system wherein my invention has been embodied; and Fig. 2 illustrates a modification in the arrangement for producing movement of the liquid electrode.

The system illustrated by Fig. 1 comprises alternating current terminals 10 and direct current terminals 11 which are interconnected through a main transformer 12 and a vapor electric device 13 provided with a mercury cathode 14, a starting electrode 15, a pair of exciting electrodes 17 and a pair of main anodes 18. The main transformer 12 includes a primary winding 19 which is connected to the alternating current circuit 10 and a. secondary winding 20 provided with end terminals which are connected to the anodes 18 of the device 13 and with an inter mediate terminal 21 which is connected to one terminal of the direct current circuit 11. The cathode 14 of the device 13 is connected to the other terminal 11 of the direct current circuit.

The transformer 12 is provided with a tertiary winding 22 for the purpose of controlling the starting and excitation of the device 13. The winding 22 is provided with end terminals which are connected to the exciting electrodes 17 of the device 13 through reactors 23, with an intermediate terminal 24 which is connected to the cathode 14, and with an intermediate terminal 25 which is connected to the starting electrode 15 through a resistor 26 and an operating coil 27 of a switch 28. The switch 28 is also provided with an operating coil 29 which is connected between one of the reactors 23 and one of the exciting electrodes 17.

The switch 28 is arranged to control the connection between the primary winding 19 and a pair of coils 30 and 31 one of which is connected in series with a reactor 32. The efl'ect of these coils is to produce mechanical rotation of the cathode 14 so that it is moved outwardly by centrifugal force and is brought into temporar contact with the starting electrode 15. ince the purpose of the reactor 32 is to produce shiftin or movement of the magnetic field applied to the cathode 14 through the coils 30 and 31, it may be replaced by a polyphase arrangement of coils. Such an arrangement is illustrated by Fig. 2, wherein the polyphase coils 33, 34 and 35 are illustrated as surrounding the cathode vessel and as connected to polyphase terminals 36.

The operation of the apparatus will be understood if it is assumed that the switch 28 is biased to its closed position. When this switch is closed and the coils 30 and 31 are energized, the mercury cathode 14 is rotated by the magnetic field of the coils 30 and 31 and, due to the centrifugal force produced by its rotation, it is brought into temporary con-.

the switch 28 is opened, the coils 30 and 31 are deenergized the rotational movement of the mercury cathode is decelerated, the cathode is separated from the starting electrode 5 and an arc is produced between the cathode and the starting electrode. This are is immediately transferred to the exciting electrodes 17 and the switch 28 is maintained in its open position b the coil 29. Should the starting are not be transferred to the exciting electrode 17, the operation just described is repeated due to movement of the switch 28 into its closed position. When the arc is established at the exciting electrode 15 17 the main arc to the anodes 18 is readily established and maintained.

What I claim as new and desire to secure by Letters Patent of the United States, is: 1. The combination of an electric discharge device provided with a liquid electrode, a startin electrode, an exciting electrode and a mam anode, means for producing a magnetic field whereby said cathode is rotated and brought'into contact with said starting electrode, means res onsive to said contact for deenergizing said magnetic field producing means, and means res onsive to the current of said exciting electro e for reventing reenergization of said magnetic eld producing means.

2. The combination of an electric discharge device provided with a liquid cathode and a starting electrode and with an electrode to which the starting arc is transferred from said starting electrode, magnetic means for producing rotation of said cathode, means for controlling the energization of said magnetic control means, and means responsive to contact between said cathode and starting electrode and to the current of said electrode to which the starting arc is transferred for controlling the operation of said control means.

3. An electric discharge device provided with a liquid cathode and a starting electrode and with a third electrode, said starting electrode being adapted to initiate an are be-- tween said cathode and, said third electrode, a plurality of coils for producing a ma etic field whereby said cathode is rotate and brought into temporary contact with said starting electrode, means for controlling the energization of said coils, and means responsive to contact between said cathode and starting electrode and to the current of said. third electrode for controlling the operation of said energization control'means.

In witness whereof I have hereunto set my hand this 27th day of December, 1929.

' HAROLD M. MARTIN. 

